WASHINGTON (Reuters) - Smoking marijuana, much like smoking
tobacco, may increase a person's risk for gum disease that can
lead to tooth loss, researchers said on Tuesday.

A study of 903 New Zealanders found that people who smoked
marijuana frequently had triple the risk for severe gum disease
and a 60 percent higher risk for a milder form of it compared
to people who did not smoke the drug, also called cannabis.

People who smoked marijuana less frequently had a smaller
increased risk for gum disease, the researchers said.

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Gum or periodontal disease is an infection of the tissues
surrounding and supporting the teeth. In advanced stages, the
gums and bone that support the teeth can become seriously
damaged and the teeth can become loose, fall out or have to be
removed.

"While it has been known for a few years that tobacco
smoking is bad for the periodontal (gum) tissues, no one has
investigated whether any other type of smoking is also a risk
factor," W. Murray Thomson, a professor of dental public health
at the University of Otago in New Zealand, said by e-mail.

"We suspected we would indeed find that cannabis smoking
was a risk factor, but what surprised us was the strength of
the relationship," added Thomson, who led the study published
in the Journal of the American Medical Association.

His team tracked a group of people in Dunedin, New Zealand,
since their births in 1972 and 1973. They were age 32 when the
researchers identified the "strong association" between
marijuana use and gum disease.

The researchers defined heavy marijuana users as those who
reported smoking it an average of 41 or more times annually
between ages 18 and 32 -- almost once a week.

Many heavy marijuana users also were tobacco smokers, but
the researchers said their statistical analysis showed that
marijuana increased the risk for gum disease separate and apart
from tobacco use.

"Cannabis smoking appears to have an effect which is not
far behind that of tobacco," Thomson said.

Thomson said the study adds to the understanding of health
consequences from smoking marijuana. "We already knew that it
had respiratory and mental health effects on some people, but
this is a totally new angle on its effects," Thomson added.

Researchers think tobacco smoking can lead to periodontal
disease by interfering with immune function, inflammatory
response and blood flow in the gums. Thomson said he thinks
marijuana smoking may act in a similar way.

James Beck of the University of North Carolina School of
Dentistry, who also worked on the study, said he hopes further
research is conducted to confirm a link between marijuana and
gum disease.

A U.S. group supporting legal sales and regulation of
marijuana faulted the study. "I think they've raised an
interesting question, but I don't think they're close to giving
a meaningful answer," Marijuana Policy Project spokesman Bruce
Mirken said.

Mirken called the study's definition of heavy marijuana use
arbitrary and said additional factors like alcohol or other
drug use may help account for the findings.